Transformer.



F. M. SLOUGH. TRANSFIORMER. APPLICATION FILED 81121211, 1907.

937,877, Patented Oct. 26, 1909.

2 SHEETS-SHEET 1.

P. M. SLOUGH.

TRANSFDRMEB.

APPLICATION FILED snr'nn, 1907.

937,877. Patented 0ct.26,19o9.

2 sa 'rs-s111251 a.

UNITED Asfia'rns 'PATENT OFFICE.

1L SLQUGH, 0F ELYBIA., 0R10, ASBIGNOB '1.0 DEAN ELECTRIC COMPANY, 0F DHIO, A CORPORATION 0F OHIO.

Specification of Letten Patent.

Patented Oct. 26, 1909.

To all lwhom it may concern:

Be it` known that I, FRANK M. Snouorn citizen of the United States, residing at Elyria, in the count of Lorain and State of Ohio, have invente a certain new and u seful Im rovement in Transformers, of which the fo owing is a full, clear, concise, and exact description, reference being had to the accompan g drawings, forminga part of this specitlilchltion.

My invention relates to telephone signaling systems, particularly to the ringing current producing mechanism therefor.

My invention is particularly adaptable selective systems which employ harmonic converters or polarity chauers for transforming direct current into ternating current, and in which transformers are for transforming the 'produced alternating current into alternating current of proper voltage for service. When these polarity changersl are in operation, contacts are repeatedlyl opened and closed to cause alternat' current flow through the primary win of the transformer from a current battery, and to reduce or to prevent arking the contact pointsof the polarity c angers, is usual to connect a condenser across thpriinary win This use of the condenser together wi the repeated opening and closing of the polarity changer contacts results in irregularities in the cnr rent produced in the secondary windin The result is, instead of an eicient smoo sine wave current How through the secondary winding and signaling circuit, the wave form of the secondary current is distorted. This irregular current flow manifests itself as disturbing noises in the telephone circuits whose conductors arallel the conductors conveying the secon ary aling current, these noises being parti rly noticeable and disagreeable in the operator s tele hone set.

Tie main purpose of my invention is to remedy these disturbing factors and to roduce a current flow through the secon ary winding which is in accordance with a smooth sine curve,- and I accomplish this hy an improved arrangement of the transformer magnetic circuit and windings and an improved arrangement of the condenser mechanism.

The usual arrangement of transformers is to place both the primary and secondary windings of the transformer on the same limb or section of the transformer core, the windin being usually superposed, the result being that whatever wave forms are produced in the primary winding are faithully produced in .the secondary winding together with all irregularities and disturbelements.

accordance with muilnvention, VI separate the secondary win g from the primary winding to permit' more or less mag netic leakage between such windings from the core of the transformer. The eiect of this magnetic leakage upon the wave form of the electromotive force induced in the seconda winding is to smooth ont the irregularities that would otherwise be caused by the irregular wave form of the electromotive force impressed upon the terminals of the winding, and to produce a wave orin of electromotive force more nearly in accord with a sine wave.

It is particularly desirable in connection with telephone party-line signaling systems to use n n eleetrcmotive force of sine wave form, since the apparatus which is best adapted for party lne g for use at subscribers stations is what is known as harmonic ringers, that is, ringers in which the vibrating part is tuned to respond only to a partie ai'- rate or frequency of alternating current when impressed upon such rinlgler. These ers, 1t has been found, wh e they respon best to the exact frequency for which they are tuned, will also nd, but less eectivel for a sli ht variation either above. or low the requency for which the are designed. It -has also been found that t e range of responsiveness is less with an alternating current of sine wave form than with any other form of alternating current wave, and that this with the fJI 65 the above describ supplied to the signaling circuit to as nearly a eine wave as it should be noted that the reluctance offers to the iow of magnetic flux b the core of the transformer is de dent argely upon the rate of cha e o the magneto motive force; that is, if

value in a com aratively small portion-of the cycle, the re uctance offered to the ma netic flux is much greater proportion y than if the time interval we re larger. This effect is due to the hysteresis and magnetic lag of the material of which the core is coinand in my improved constructionJ I make use of this roperty to force a portion of the magnetic ux across the air gap between the two windings of the transformer from one portion of the core to another, and thus to cause, momentarily, an abnormal amount of m etic leakage between such windings. In way the induction in the secondary winding, which would result from the abnormally high value of the current at the start of the cycle, is avoided, and the eiect is to reduce an induced electromotive force in tige secondary winding of nearly sine form.

Inconnectionwith l changerait hasbeenfounddesraleto ridgeacondenser across thrtaehrins of the primtg to neu e sparking" woutlrla otherwise take placei auhe cintacts on polarity changer, an con enser, Iiind,canheusedtomaterial1yassistiii the form of wave of the imw ectromotive force. Howjever if epended upon alone to produce this effect, it would not be suicient. I also find it desirable, under certain circumstances, to make use of a. condenser bridged across the terminals of the secondary winding of the transformer, and find that by means of the en t of win and condensei-s above described, when t en together, I am able to produce an electromotive force in the secon winding of practicall sine wave form. In this connection, it sho d be noted, however, that it is not practicable to use a condenser in connection with the secon winding that will entirely produce this m fication in wave form since this would result in serious phase displacement and incread tendency toward sparking at the vibrator contacts in the primary circuit. I also tprovide means for normally disconnecting e condenser bri ed across the seconda terminals from su secondary winding, 1v en the transformer is not in use, as a result if whiclidfir nl loadnditions the curren r uir e rima winding of the traiiformer {vill nog be elaycessive. have found it desirable to provide means for readily adjustin the airgalp over which magnetic eakage takes possible. In this connectioni e magnetzing current in. creases from a zero va ue to its maximumlace order that different conditions oun in racticemay readily be met by means of t e same transformer.

The several drawings illustrating iiiy in ventionare as follows:

Figure 1 illustrates the usual arrangement of windings and core in transformers; Fig. 2 shows an arrangement of these parts in accordance with my invention; Fi 3 diagrammatically illustrates the curve o the electromotive force of the primary of the transformer of Fig. 1; Fig. 4 di 1u u tically illustrates the electromotive orce curve of the secondary of the transformer ofv Fig. 1; Fig. 5 represents the sine curve of the electrpmotive force and current of the secondary win of the transformer in Fig.- 2, 'and llg.6 i L Il nticllylllllstlteselective signaling system, showing the adaptation of my improved transformer.

Fig. 1 represents one of the usual transformers now used. The magnet corel is ihult up of rectangular lamintions having erectangularo 2an 3cut therein to leave the celiientrallgiiemher 4 on which are mounted both the rimary winding 5 and the secondary winding 6, usuali superimposed upon each other, the coils so close to each other that the in etic ux caused by current now through tlzhgixalprima winding would also through the secon ary winding, inclu the magnetic dow due to the superimfposed irregularities, and the electromotive orce and current curves in the secondary winding will be distorted as shown in Figs. 3 and 4, the wave forms shown beingatraced by means of the oscillo- Eraph and ithfully showing the exact beavior of electromotive force and current for thearra tshowninF' .1. The superimposed irregular magnetic anges are very rapid in action and will follow the path of least resistance, and this ath in the transformer shown in Fig. 1 include the core surrounded both windings. In Fig. 2, however, an improved a ment in accordance with my invention is shown, the iaminations bein Y rectangulr form and ving a centra ope t primary winding 5 encircling 8 at the'end of the core and the secondary winding 6 encirclin' the etentghh other of the core. wingto is enin o ecore and the relative location of te windings thereof, there is great increase in the inagnetic reluctance of the core and a tendency for the magnetic flux to go in part between the windings from one portion of the core to the other, especially when the rate of change of the m a result e impressed electromotve force and current waves will be modified, for reasons already indicated, and will a pear in the secondary winding in the form indicated in Fig. 5, that is, for this form of core and eto motive force is rapid, and as 125 sans?? 3 relation of windings,the path of least reluctance for a portion of the magnetic flux will be from one part of the transformer core to another, andthis path will lie between the 5 win of the transformer, as aresult of 'which ie extreme effect of the ra id change in the magneto motive force in t e rimary wind' is avoided, and the wave orme of the current and elcctromotive force inthe secondary winding are made to approximate a sine wave form.

In Fi 6 a selective signaling circuit is shown, owing the ad'pltability of my improved transformer. e party telephone ine L is shown as supplying two arty substations represented by signal bel a and b, this line terminating at the central eirch C in ri jack J. The cord circuit at e centra exc ngecoinpris the tip end sleeye strands t and s respectively, terminating in the lu p. Connected w1th tip strands are t e ey springs correspond in number to the number of parties on the e-in this case, 2-and represented b ka and kb. The companion spring m rs Isc and kd connect with a common grounded conductor 10. Contact 11 for key ka connects through conductor 12 with e secondary windi 6 of transformer Ta, while contact ao 13 for spring kb connects through conductor 14 with the secondary windin of transformer Tb, the other terminal o the transformer being grounded. Thus, if the first selective key is depressed, current generated in the secondary windi will ilow through the following circuit; om the secondary winding of transformer Ta, through conductor 12 to contact 11, key spring ka, tip of plug p, through thpsring )ack and line L, through the s ala and b,

the sleeve side o the line and cord circuit, through spring 15 and contact 16 of the master ke K to ground, and thence to the groun ed terminal of the secondary winding of transformer Ta, this master key bei U actuated to disconnect the key om the remainder of the cord circuit for well known reasons. For each transformer there is provided a polarity changer driven direct current flow from a main battery for transforming the direct current into alternatingr current flow through the primary winding of the transformer.

Each polarity cha -r is controlled by a 55 relay Ra. Contact 17 or key spring kc connects throu h conductor 18 with one terminal of t e relay whose other terminal connects through conductor 19 with one terminal ot the battery B whose other terminal 5C is ounded. In the same manner, contact 20 or spring kd connects through conductor 21 with one terminal of relay Rb whose other terminal connects through conductor 22 with the main battery. Thus, upon depression of the firstselective key, current will dow from battery B through conductor 19, relay Ra, conductor 18, contact 17, sgi-m5 kc and through conductor 10 to groan en thence to the grounded terminal of the bat- Armature r of the rela Ra is connected with conductor 18, whi e its contact 22 connects tlirough conductor 23 with the amature 24 of the polarity chang-tier. Each armature carries a weight 25 w 'ch es the rate of vibration of the armature and thus the frequency of the current produced. Contact 26 carried by armature 24.- normally engages contact 27 connected through conductor 28 with one ter mina-l of the winding of the electro-magnet 29, the other terminal of this winding being grounded. Upon attraction of armature r, current flows from the main battery, through conductor 19, armature r, through conductor 23, contacts 26 and 27, conductor 85 28, and through electromagnet 29, causing attraction of armature 2t and disengagement of contacts 26 and 27. This disengagement of contacts 26 and 27 ruptures the circuit through electromagnet 29, and armature 24 being released, again engages contact 26 with contact 27 to cause closure of the circuit through electroni et 29 and'attraction of armature 24 to disrupt the circuit, and so on, the result eing vibration of armature 24 on the well known rheotome principle. Armature 24 carries a sp 30 having electrical contact therewith an a spring 31 insulated therefrom and connected with ground. The outer contacts 32 and 33 are associated with springs 30 and 31 respectivel and are connected by conductors 34 whic connects with one terminal of the primary winding of the transformer. The inner contacts 35 and 36 for the spr' 30 and 31 are connected together and wi the other terminal of the primary Thus, when the amature is attract springs 30 and 31 will be carried into engagement with contacts 35 and 33 respectively, causing current ilow from the battery through armature r, conductor 23, armature 24, spring 30, contact 35, primary winding, contact 33, and spring 31 to und, the current flow being through t e rimary winding in one direction. Upon re ease of the armature springs 30 and 31 are thrown against contacts 32 and 36 respectively, and current flowing to armature 24 flows through spring 30, contact 32, conductor 34, primaryr winding, contact 36, and spring 31 to ground, the direction of current liow through the primary winding being in the opposite direction, and thus upon vibration of the nrmature 24, alternatin current flow will be produced through t e primary winding which will be induced into the secondary windin A suitable condenser c is usually brid across contacts 26 and 27 to Euclavcnt spar 'ng, and also to prevent spar g at 130 the lari changer contacts a condenser c is ulallytyemployed bridged between the primary erminals.

The combination of m improved transformer arrangement an the condenser c' tends to eliminate all irregular and disturbing elements from the secondary circuit yand to produce current flow along a smooth sine curve which form of current ilow .is adapted and safest for uses in selective sigsystems. As the polarity are during the greater part ofthe time uuder no load conditions, the condenser o 1s preferably designed to prevent sparking at the polarity changer contacts under such no load conditions When, however, current flows through the secondary wm 0' and circuit, the condenser is no lo a le to suppre all the sparking, and nd that sparking can be entirely prevented under working conditions by bri a condenser d' about the secondary I find that the use of this condenser across the second arywindingalsoassistsinsmoothingout the wave form and through which reaction on the primary circuit of the transformer greatly improves the operation of the polaror converter.

One of the advantages of a condenser across the secondary circuit is to take u the high voltage discharges due to the rapi drop in magnetization when the circuit in the primary is abruptly opened. These high voltage discharges, unies suppressed, are suicient under certain circumstances to puncture the insulation of the switchboard conductors and other apparatus connected with the ringing circuit. The condenser d' should, however, be carefully adjusted. Where the secondary current used is not v heavy, a condenser of small capacity d be used and could be bridged directly across the secondary terminals without seriously influencing the operation of the converter under no load conditions.

When the current in the secondary circuit is to be heavy, a larger capacity condenser, of course, must be used across the secondary in order to suppress the at the converter contacts, and if the condenser were bridged directly across the secondary winding, a he'avy load would be placed on. the prim' ary winding under no load conditions.

t is, therefore, preferable, when a lar e capacity condenser is used, to provide or disconnecting the condenser from circuit under no load conditions. One wa of accomthis would be to inclu e the windings o a relay w' in the secondary circuit of the transformer, the connection of one terminal of the condenser d with the secv ondary winding being controlled by the armature y' and contact e of the rela Normally the condenser circuit is o en, ut u on depression of a ringing key, t e secon ary circuit is closed, and mirrent flow through therelay causes attraction of its armature and closure of the condenser circuittlie con. denser d then becoming eiiective. There.

la used in this case should preferably be' o the slow type, in order that it may not be vibra by the alternating current 1n the secondary circuit and thereby cause arcing at the contact e'. Other ways, of course, could be readilydevised for causmg the secondary condenser 'to be effective only when. ug current is to be used. In anarrangement like there will be no sparlnng'at the converter contacts under no load conditions nor under operating conditions when ringing current is bein used, and the condensers and the ormer 'winding arrangement mutually assist each other to prevent such sparking and to improve the action of the transformer to give the proper form o f alternating current wave.

As shown m Fig. 2, I provide means for varying the amount of magnetic leakage above described, which I have found desirable to meet the various conditions found in practice, so that the same desi transformer may be used to meet these ierent conditions. This consists, as indicated, in roviding an ad ustable member 37 in one of the ormer by means of which the air-gap 1n the leakage path may be increased or as desired A clamping screw 38 1s provided'to secure the member 37 in an desired ad]ustment.

aving described m invention, I desire to secure by Letters atent the following claims:

1. In .a signaling system2 in combination with sultable receiving apparatus, a source of signaling current, a polarity changer connected to such source of current, a transformer havinghprimary and secondary such po rity changer adapted to intermittently supply current from such source to such primary windin such secondary winding connected to suc signal receiving ap aratus, and means for automatically inclu ing reactive means in circuit with the seconda winding when current is delivered from such secondary win 2. In a si ling systemz in com ination with suitab e signal receiving apparatusz a source of signaling current, a polarity changer connected to such source of current, a transformer havin primary and secondary windings, such po rity changer adapted to intermittently supply current from such source to such primary winding? such secondary winding connected to suc signal receiving aplparatus, and means for automatically inclu ing reactive means in circuit with the secondary winding when the current flowing in the secondary winding reaches a predetermined strength.

3. In a signaling system, in combination with suitable signal receiving apparatus, a

source of signaling current, a polaritychanger connected to such source of current, a transformer having primary and secondary windi such polarity changer adapted to intermittently supply current from such souice to such primary win s uchsecondary winding connected to su signal re ceiving apparatus, reactive means no rinally disconnected from such secondary winding), and'ineans for automatically including suc reactivemeans in circuit with the secondary Finding when current is delivered therem. 4. In a signaling system, in combination with suitable signal receiving apparatus, a source of signaling current, a polarity changer connected to such source of current, a transformer havi primary and secondary windings, such po arity changer adapted to intermittently supply current from such source to such primary wind such secondary winding connected to suc signal receiving apparatus, reactive means normally disconnected from such secondary and means for automatically including suc reactive means in circuit with the seconda winding w en the current flowing in su secondary winding reaches a predetermined stren h. b

5. na a` stem,incom ination with snitallnsihlagl apparatus, a source of signaling current, a polarity changer connected to such source of current, a transformer ha primary and secondary windings` such polarity changer adapted to intermittently supply current from such source to such primary wind' such sec` en dniy winding connected to suc signal-re ceiving algaratus, a condenser normally disconnect from such secondary winding and means for automatically connec such condenser across the terminals of suc secondary winding when current is delivered therefrom.

6. In a signaling system, in combination with suitable signal receiving apparatusz a source of signaling current, a polarity changer connected to such source of current, atransformer hav' primary and secondary windings, such llilarity changer adapted to intermittently supply currentfrom such source to such primary winding, such secondary winding connected to such signal receiving a aratns, a condenser normally disconnect om such secondary winding, and a relay connected with such secondary winding adapted to automatically connect such condenser across the terminals of such seconda winding when current is delivered there m.

'i'. In a telephone system, a central ollice, line wires extending therefrom to a suhscribers station, signal receiving apparatus at such subscribers station, asource of signalingY current at such central cnice, larity changer connected to such current, a' transformer hav primary and secondary windings, such arity changer adaptedto supply current rom such source periodically in reversed directions to such primary windings, means for inducing an electromotive force of practically sine wave form in such secondary winding compri in part a condenser normally disconnclld from such secondary windi and adapted to be automaticall connecte to the terminals of such win when current is delivered therefrom, alii means for supplying the current induced in such secondary winding to such line wires.

8. In a telephone system, a central oice, line wires extending therefrom to a subscribers station, signal receiving apparatus at such subscribers station, a source of signaling current at such central oiice, a polarity changer connected to such source of current, a transformer ha primary and secondary windings, such larity changer adapted to supply current om such source periodically in reversed directions to such primary winding, means for inducing an electromotive force of practically sine wave form in such secondary winding comprisin in part a condenser normally disconnecte from such secondary win and adapted to be automaticall connecte to the terminals of such win when current is delivered therefrom, a second condenser connected across the terminals of the primary win of Such transformer and in so loeating t e windings on such transformer as to (permit magnetic leakage between them, an means for supplying the current induced in such secondary winding to such line wires.

9. In a telephone system, a central ollice, line wires extending therefrom to a subscribers station, signal receiving apparatus at such subscriber-s station, a source of signaling current at such central oiiice, a polarity changer connected to such source of current, a transformer ha primary and secondary windings, such arity changer adapted to supply current roui such source periodically in reversed directions such primary winding, means for inducing an electromotive force of practically sine wave form in such secondary winding comprising in part a condenser normally disconnects from such secondary winding and a relay in circuit with such secon ary winding adapted to automatically connect such condenser to the terminals of such windin when current is delivered therefrom, an means for supplyin the current induced in such secondary win ing to such line wires.

10. In a telephone system, a central oflce, line wires extending therefrom to a subscribers station, signal receiving apparatus a posource of .the .ternuv a --..11!d. l41g1 `fs\.1jhfuans y y Y y, wawtmg'thef-windingon 5 -Sewndary wlndmgsf-Suchrs .rltyicbngefy"fmlha:tfmliflr .fasrweg mit magnetic 20 gdaptefl tosuv'pplycurrent` 4A omslrxch-'som-'ce'i L-lGkgQ betwenrtlim melhs for su pegldlcally m reverseddrec'tions 1:o^su ,:h` plyingt e' cumul: mlucd'in'suchsecon Pnmary winding; means fQr-aindycng isn' "windingitf-suchfliheiwirw electlf'motivejforce-ofprgcnz;illyisixejfig'cfnvexv Wh4 f' Iherunto subscribe 10\.f;fo'1'm such secondary mndmgcomprlvsm -my .name this 221i ,Zy AugstfA; D. 25 in part@ condsnser normally tl'isuforvrl;- 1907. -f imm such secondary `and. a relay FRANK M. SLOUGH. in circuit with such secon ary wzwrindln'g.V Witnesses: adapted to automatically connect snel; -cpn- RAY H. MANsoN, 15 denser to the terminals of suchwxndmg GEO. SoovxLLs. 

